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GRAND CHALLENGE 3:
Design a Future
Without Pollution or
Waste
In nature, waste is a resource. One organismâs waste is
repurposed to sustain another. Since the Industrial Revolution,
human society has adopted a more linear model. Resources and
energy are used to manufacture products, which are then used and
ultimately discarded as waste when those products are no longer wanted
(Figure 3-1). This linear model of âtake-make-wasteâ has been successful in
providing affordable products to billions of people and advancing their standard of
living. However, this production model generates over a billion tons of discarded
products and by-products globally each year (see Box 3-1), and uses large amounts
of energy and resources that are never recaptured. An analysis of five high-income
countries found that one-half to three-quarters of annual resource inputs are
returned to the environment as wastes within a year.159 Despite improved efficiency
in the use of resources, the overall production of waste in many countries,
including the United States, continues to increase.160
The âtake-make-wasteâ model introduces large amounts of pollutants into the
water, soil, and air. Throughout much of the 20th century, large-scale chemical
production combined with inappropriate chemical handling and waste disposal
created a daunting array of legacy hazardous waste sites globally.165 Technologies
to characterize these sites and contain and remove hazardous contaminants have
advanced significantly over the past three decades, and there have been many
successes.166 However, there remain at least 126,000 hazardous waste sites with
residual contamination in the United States alone, about 12,000 of which are
considered unlikely to be remediated to the point of unrestricted use with current
technology. Some of these sites will require monitoring, treatment, and oversight
in perpetuity.167 Meanwhile, new concerns associated with legacy contaminants
continue to be discovered (Box 3-2).
FIGURE 3-1.â The linear model of resource extraction, manufacturing,
consumption, and disposal (âTake-make-wasteâ) dominates global
economies. This model produces ever-increasing amounts of garbage
while wasting resources and generating excess pollution. NATURAL RESOURCE EXTRACTION
44â ENVIRONMENTAL ENGINEERING IN THE 21st CENTURY:â ADDRESSING THE GRAND CHALLENGES
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BOX 3-1. RETHINKING CONSUMPTION ability to be reused, recycled, or biodegraded.161 Municipal solid
AND WASTE waste generated per year is expected to double by 2025162 and
Energy, water, and food resources are routinely wasted triple by 2100.163 This upward trajectory is occurring despite
along supply chains. For example, food waste includes increases in recycling and reuse in the developed world
harvest spillage or damage, losses during processing, and primarily because the increasing size of the middle class, which
produce thrown away because of blemishes or spoilage (see accounts for the bulk of consumer goods spending (Figure).
Challenge 1). For computers and other electronic devices, In 2015, there were more than 3 billion people in the middle
waste is generated from mining raw materials and from class worldwide, and by 2030, the middle class is anticipated
manufacturing processes. Once in use, many end products to expand by another 2 billion people.164 Much of this growth is
do not take long to become waste themselves. The plastic in the developing world, where modern environmentally sound
sandwich bag that is manufactured from petroleum or the methods to manage waste are less common. Encouraging less
foil wrapper derived from refined bauxite ore are often used consumption, developing product designs and manufacturing
for a matter of hours before being discarded. The service life that minimizes waste, and increasing recycling and reuse
of electronic products continues to shrink due to technical globally is a major opportunity and responsibility of the
advancement, style preferences, or planned obsolescence. environmental engineer that will preserve resources for future
Globally, about 80 percent of consumer goods, excluding generations and reduce waste and pollution.
packaging, are disposed after a single use with no plan or
FIGURE â Current and projected urban waste generation by income level and year.
PRODUCTION & CONSUMPTION WASTE & POLLUTION
Design a Future Without Pollution or Wasteâ |â 45

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BOX 3-2. EMERGING CHALLENGES WITH LEGACY combined with insufficient environmental protection over
CONTAMINATION the past three decades has resulted in widespread soil
New concerns associated with legacy contaminants contamination. Chinaâs first national soil survey results
continue to be discovered. For example, per- and are alarming: nearly 20 percent of agricultural lands
polyfluoroalkyl substances (PFAS), which include over 3,000 are classified as polluted.187 The pollution stems from
compounds, have been produced worldwide since the atmospheric deposition of heavy metals and direct irrigation
1940s for use as water-resistant coatings in manufacturing using industrial wastewater,188 and human exposure is
and in fire-fighting foams commonly used at military and evidenced by heavy metal contamination in Chinaâs rice
civilian airports.183 Over the past decade, these chemicals, crop.189 The scale of environmental cleanup needed to
sometimes called âforever chemicalsâ because they do not address this problem is similarly alarming, with cost
biodegrade, have been increasingly detected in surface estimates of Chinaâs current land remediation plan as much
water and groundwater, sometimes at levels exceeding as $69 billion by 2020.190
the U.S. Environmental Protection Agencyâs (EPAâs) Environmental engineers can help address legacy
lifetime health advisory level (70 ng/L, established based contamination problems using sustainable remediation
on exposure to two PFAS compounds).184 Based on EPA approaches. These include stakeholder engagement and
sampling of public water supplies in the United States, up life-cycle analysis to identify the best long-term solutions
to 15 million people live in areas where their drinking water that are socially acceptable and economically viable while
exceeds the EPA health advisory level.185 However, in mid- minimizing negative side effects of cleanup activities, such
2018, the Agency for Toxic Substances and Disease Registry as air pollution and ecosystem degradation.191
in a draft toxicology risk assessment stated that the EPA
level may be 7 to 10 times too high for two common PFAS
compounds to protect against health risks.186 Continued
research is needed to determine the scope of the problem,
assess the risks posed by the many different chemicals,
and develop water treatment options where appropriate to
inform policy decisions for use and management of these
compounds.
Rapidly developing countries are also facing escalating
environmental crises as a consequence of major economic
growth without regard for socioenvironmental costs.
A key example is China, where industrial development
Over the past few decades, the amount of pollution produced by some industries
and activities has dropped precipitously thanks to research and technology
advances and effective policy interventions (see Challenge 5). For example,
regulations on heavy-duty diesel fuel emissions, the development of ultra-low-
sulfur diesel fuel, and new emission control technologies have helped reduce
particulate matter and nitrogen oxide emissions by more than 90 percent in
diesel truck and bus engines put into use since 2010 in the United States.168
Nevertheless, large quantities of untreated sewage, industrial by-products, and
vehicle emissions continue to find their way into the water, soil, and air.169 Human
activities are causing nitrogen and phosphorus to accumulate in bodies of water170
and greenhouse gases to accumulate in the atmosphere (see Challenge 2).171 Toxic
chemicals have been detected in people and wildlife in every corner of the globe,
from the Arctic wilderness to remote tropical islands.172
Because of improvements in living conditions, including water treatment, sanitation,
and health care, the 20th century saw a doubling of life spans globally,173 but
pollution continues to have profound effects on human health. Pollution contributes
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12
Global attributable deaths (millions)
10
8
6
4
2
0
FIGURE 3-2.â Global estimated deaths by risk factor and by total environmental and occupational causes (blue),
which are disaggregated and shown individually in purple. Air pollutionâattributable deaths are primarily linked
to particulate matter pollution and indoor burning of solid fuels. Water-related risks are associated with diarrheal
disease from unsafe water and poor sanitation. The estimated occupational deaths include 0.33 million from injury,
but the remainder are from pollution-related causes, such as asbestos, carcinogens, and airborne particulate matter.
The risk factors are not exclusive of one another.
to the leading causes of death worldwide including heart disease, stroke, and chronic
lung disease. One of every six deaths in 2015âabout 9 million deaths worldwideâ
can be attributed to disease from exposure to pollution (Figure 3-2).174 Air pollution
causes two-thirds of the premature pollution-related deaths, while unsafe drinking
water and sanitation account for nearly 20 percent.175 More than 90 percent of the
worldâs population lives in areas where air quality does not meet health standards.176
Although the problems are worse in low- and middle-income countries where
the sources of air pollution are minimally controlled, air pollution is estimated
to cause nearly 400,000 premature deaths annually in high-income countries.177
Because these estimates do not account for compounds whose effects are not well
characterized, for example, chemicals thought to cause endocrine disruption, the true
toll of the health effects of chemicals is likely underestimated.
Pollution also harms natural ecosystems. Metals leaching into streams from
abandoned mines have been linked with reduced biodiversity, and trace organic
chemicals, such as pharmaceuticals, have been associated with reproductive
anomalies including the feminization of male fish.178 Millions of tons of plastic end
up in the oceans every year,179 creating large floating islands of garbage, and small
plastic particles (âmicroplasticsâ) are accumulating in the food chain with a largely
unknown effect.180 Wastewater discharges, urban and agricultural runoff, and fossil
fuel combustion sources have overloaded lakes, estuaries, and rivers with nutrients,
fostering algal blooms that can deplete oxygen and produce toxins.181 All of these
ecological problems ultimately harm human health and disrupt industries such as
fisheries and agriculture. In 2014, for example, about 500,000 residents of Toledo,
Ohio, were ordered not to use their tap water for days due to toxins produced by an
algal bloom in Lake Erie.182
Design a Future Without Pollution or Wasteâ |â 47

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Challenges posed by pollution and waste will intensify as the worldâs population
grows, people live in ever higher densities, standards of living increase, and
industrial production expands to meet increasing demands. Two new approaches
will be required to achieve economic progress while minimizing negative health
and environmental impacts and sustainably managing Earthâs resources. First, a new
paradigm of waste management and pollution prevention is neededâone that shifts
from a linear model of resource extraction, production, use, disposal, and cleanup
toward one designed to prevent waste and pollution from the outset. Second,
innovative approaches are needed to recover valuable resources from the waste we
do produce. Ideally the two approaches are closely coupled. These new approaches
will require life-cycle and systems thinking to identify sustainable solutions that
minimize the amount of energy and resources consumed and the amount of waste
and pollution generated through all components of production and use.
Preventing Pollution and Waste
Through Improved Design
Every day, new chemicals and materials are manufactured, elements are mined from
the earth, fuels are burned, and fertilizers and pesticides are made and used. These
activities are undertaken to support functions and provide servicesâsuch as the
production of food, medicines, clothing, building materials, and electronicsâthat are
vital to our society and economy. The question is now how to provide these functions
and services without generating the types and scale of pollution and waste that have
harmed human health and ecosystems in the past.
The solution requires working toward a circular economy designed to prevent
harmful waste and pollution from the outset. Within a circular economy, processes
are designed to minimize waste, products and waste materials are reused if
possible, and materials that cannot be reused are remanufactured or recycled
(Figure 3-3). Organic wastes that cannot be reused are converted to other useful
products such as chemicals, materials, or fuels. Pollution prevention is also
considered at every design stage to minimize negative impacts. Using materials
48â ENVIRONMENTAL ENGINEERING IN THE 21st CENTURY:â ADDRESSING THE GRAND CHALLENGES
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urce efficiency an
r reso d to
sign fo min
De im
ize
po
Re
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on
ib
le
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s
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Sourcing y recovery
Landfi erg
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ra
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ate
Comp
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benign in the environment reduces
Design for r
risks to human and ecosystem
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the economy and society. When
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considering the entire life cycle,
designs that reduce energy use and
De
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promote efficiency are emphasized.
sig
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By thinking beyond incremental
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new approaches that eliminate waste and n fo or repa
ir Desi
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pollution, environmental engineers can help achieve
a sustainable future.
FIGURE 3-3 Sharply reducing waste and
Design is the stage that most influences the types and pollution requires new approaches to design
amounts of waste or pollution that will be generated. based on life-cycle thinking.
At the design stage, engineers are able to help select
and evaluate the characteristics of the final outcomes,
considering material, chemical, and energy inputs;
effectiveness and efficiency; aesthetics and form; and specifications such as
quality, safety, and performance. In the development of new systems, this stage is
ideal for innovation and creativity and represents a key opportunity to integrate
environmental goals into the specifications of the products or processes. Through
life-cycle and systems thinkingâas well as green chemistry and green engineering,
which emphasize designs that ensure that inputs, outputs, and processes are as
inherently nonhazardous as possibleânew designs can be implemented that rely
on more benign materials and less energy, that do not generate much waste, and
that do not shift environmental burdens from one place to another. Benefits of such
an integrated approach include wise use of resources, improved human health,
and enhanced protection of natural systems. Advances needed to support a circular
economy include efficient and effective separation and recycling technologies
and market forces or government incentives that recognize the broader impacts of
pollution and waste (see Challenge 5).
Many of the most successful interventions focus on preventing the production or
release of pollution or waste. This strategy is generally easier and less expensive
than remediating contamination sites after toxins are dispersed in the environment.
For example, perchloroethylene, a widely used solvent for dry cleaning fabrics
and metal degreasing operations and a likely carcinogen,192 has been replaced in
these applications with supercritical carbon dioxide, which has low toxicity and is
chemically stable, readily available, and easily recyclable. Another example is the
recent movement away from subtractive manufacturing, a process by which three-
Design a Future Without Pollution or Wasteâ |â 49

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dimensional objects are constructed by successively cutting material away from a
solid block of material. Instead, additive manufacturing,for example, 3-D printing
constructs objects by successively depositing material in layers without the need to
generate waste by cutting material away. A growing number of zero-waste businesses
and communities aim to reuse, recycle, or recover at least 90 percent of discarded
material while also aiming to produce no pollutants to air, water, or land.193
Eliminating the use of the most toxic chemicals is an important part of green
design. To develop nonpolluting components and processes and prevent
future contamination, it will be important to fill knowledge gaps about the full
environmental risks of new and existing contaminants. For example, methyl-tert-
butyl ether (MTBE) was added to gasoline to help reduce emissions in vehicle
exhaust. However, MTBE became a groundwater quality problem once gasoline
leaked from underground storage tanks because MTBE was able to migrate farther
and was more resistant to biodegradation than other compounds in gasoline.194
Of the more than 140,000 new chemicals that have been introduced since 1950,
fewer than half have been subject to human safety or toxicity testing.195 EPAâs
Pollution Prevention Framework can be used to estimate physical properties,
which are then used to predict environmental concerns such as toxicity, mobility,
persistence, and bioaccumulation, but more development and validation is needed.
In addition, there are significant needs related to risk communication to help the
public and decision makers understand the true costs of pollution.
Capturing the Value of Waste
Under a linear production model, resources are used inefficiently and can become
depleted as landfills expand. Recovering resources from waste recaptures the value
of those materials and minimizes environmental impacts from further resource
extraction. Localized or distributed recovery and reuse also reduces the energy
requirements and pollution associated with transportation of materials and waste.
Resource recovery can also address local resource shortages in economically
depressed or geographically isolated communities.
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Todayâs common waste recovery efforts focus on recycling plastic, glass,
paper, aluminum, and scrap metals, but much more is possible with advances
in engineered environmental processes that allow the extraction of specific
components from waste mixtures. Precious and rare-earth metals could be retrieved
from electronic waste196 and potentially even mined from landfills. Carbon
capture systems could be used to turn carbon dioxide into forms that are useful
for applications ranging from building materials to plastics to greener solvents.197
Nutrients in wastewater could be captured for use as fertilizers (see Box 3-3).
Many of todayâs municipal and agricultural waste streams are rich in organic
carbon, which could be recovered and channeled toward chemical manufacturing
or energy recovery.198 The amount of energy contained in wastewater is equivalent
to several multiples of the amount of energy required to treat it.199 Energy recovery
has been implemented at numerous centralized wastewater treatment plants,
including in Oakland, California, and in Strass, Austria, by converting a fraction of
the incoming organic carbon to biogas to produce heat and electricity.200 However,
technologies have not yet been developed to cost-effectively capture the full
potential of the embedded energy.201
Recovery of resources from waste streams has long been practiced, but in a
nonsystematic fashion. In Dharavi, India, one of the largest slums in the world,
people have built a thriving economy, employing approximately 250,000 people,
based on recovering waste generated in Mumbai. âGobar gas,â produced from
anaerobic digestion of animal waste, is used for cooking and community-scale
lighting in rural and urban communities, particularly in Southeast Asia and sub-
Saharan Africa. Fly ash and gypsum by-products of coal combustion have been used
in the manufacturing of concrete and wallboard.207
BOX 3-3. NUTRIENT RECOVERY reserves for the future, but further advances in waste
Nutrients present in wastewater can cause problems separation are needed to achieve the technical and economic
for the environment and infrastructure, such as algal viability for widespread adoption. 205 In addition, producing
blooms in lakes and estuaries and buildup of the mineral reactive nitrogen for fertilizer from inert nitrogen gas in the
struvite in the mechanical systems of wastewater atmosphere requires a considerable amount of energy and
treatment plants. Globally, humans release about 30 creates further imbalance in the global nitrogen cycle. 206
percent more phosphorus and twice as much nitrogen Some wastewater facilities have been successful in extracting
into the environment, mostly from fertilizers, than aquatic phosphorus to create a commercial fertilizer, but in most
ecosystems can bear without degrading habitats. 202 Reusing cases, recovery of phosphorus and nitrogen from wastewater
nutrients in existing waste streams can help mitigate these using current technologies is not economically viable.
challenges while producing valuable services. For example,
reuse of municipal wastewater or agricultural runoff for
irrigation can reduce fertilizer use.
Innovative approaches to cost-effectively recover and
reuse nitrogen and phosphorus from waste streams rather
than mining new phosphorus or synthesizing new nitrogen
could conserve natural resources, reduce pollution, and save
energy. Phosphorus is an increasingly scarce natural resource
with limited mineable reserves, 203 but the phosphorus
available from human urine and feces could account for 22
percent of the global phosphorus demand. 204 Recovering
phosphorus from waste thus helps to preserve phosphorus
Design a Future Without Pollution or Wasteâ |â 51

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Resource recovery is rapidly being integrated into existing
manufacturing, agricultural, and industrial practice, but
much work remains to be done to realize its potential, both
in terms of recovery yields and the types of resources that
can be cost-effectively recovered. A significant impediment
to utilization of waste is that existing traditional waste
streams have not been systematically characterized with
resource recovery in mind. Local, regional, and global
inventories of waste materials are needed to identify
opportunities for reuse or inputs to other production
schemes. With this information, appropriate technologies
for resource recovery can then be developed using physical,
chemical, and biological processes that capture the
maximum financial, social, and environmental benefits.
This information could also lead industries to redesign
their resource extraction and manufacturing processes to reduce waste and more
efficiently and cost-effectively recover and reuse valuable resources.
Results of public programs to reduce, reuse, and recycle have been mixed. The
United States, for instance, recycles or composts 35 percent of its municipal waste
and less than 10 percent of its plastics,208 but higher rates are possible. Six countries
recycle or compost more than half of their waste, led by Germany at 65 percent and
South Korea at 59 percent.209 In 2016, nearly 48 million metric tons of electronic
waste were produced globally, representing a value of approximately $60 billion in
raw materials, and only 20 percent of this waste was recycled.210 EPA reports that
electronic waste accounts for 70 percent of heavy metals in landfills, such as mercury,
lead, and cadmium.211 Waste streams are often heterogeneous, complex mixtures
that currently require significant resources and energy to separate. Sorting technology
has been developed and commercialized for some wastes, such as separating
organic from inorganic wastes. The extent of resource recovery from wastes could be
enhanced by improved, cost-effective waste separation techniques.212
Effective waste recovery requires attention not only to scientific and engineering
capabilities but also to economic and behavioral factors. Considerations of financial
viability and feasibility include the cost of the recovery technology, the quality
of the recovered product, the market for the product, any adverse environment
impacts, and measures required to manage and prevent them. Governments can
also develop incentives to encourage waste recovery that account for broad societal
and environmental benefits of these programs (see Challenge 5).
Many of these advances are focused on large urban areas, where the highest
volumes of waste are generated. However, there is also substantial potential to
harvest the value of waste streams that are smaller or more intermittent to benefit
rural communities. For example, decentralized resource recovery systems could be
developed, particularly for sewage, food, animal, and agricultural waste.
What Environmental Engineers Can Do
With training in environmental chemistry, microbiology, hydrology, transport
processes, solid waste management, water and wastewater treatment, and air
pollutionâas well as skills in life-cycle and systems thinkingâenvironmental
engineers bring important capabilities toward designing a future without pollution
52â ENVIRONMENTAL ENGINEERING IN THE 21st CENTURY:â ADDRESSING THE GRAND CHALLENGES
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and waste (see Box 3-4). Technological advances combined with innovative new
materials and designs can be used to conserve natural resources and minimize adverse
effects on human health and the environment. These complex challenges demand
solutions that consider broad costs and benefits throughout the life cycle, including
human health risks, environmental impacts to water, soil, and air, as well as social and
financial impacts (see Challenge 5). Environmental engineers can help analyze the
impacts of innovative manufacturing and resource recovery approaches compared to
the life-cycle impacts of traditional processes to identify the most promising solutions.
For many pollutants, although the knowledge and technology exist to reduce exposure,
the greater challenges are economic, political, and social. For example, billions of
people worldwide use solid fuelâburning cookstoves for daily meal preparation,
creating large amounts of particulate matter pollution. It is possible to design cookstoves
that are much cleaner burning to benefit health, local environmental quality, and
climate, but there are cultural, economic, and logistical hurdles to their adoption.213
Improving resource recovery in developed countries may require people to change
their behaviors and accept new approaches to waste separation. An interdisciplinary
approach applying social and cultural knowledge is crucial to overcoming such hurdles
to guide the development and adoption of sustainable solutions.
BOX 3-4: EXAMPLE ROLES FOR ENVIRONMENTAL ENGINEERS TO DESIGN A FUTURE WITHOUT
POLLUTION OR WASTE
Environmental engineers have essential skills needed to move toward a future without pollution or waste. Examples of ways
environmental engineers can contribute include
Preventing Pollution and Waste:
â¢âedesign products and their production processes to promote resource efficiency, longevity, reuse, repair, and recycling
R
while minimizing pollution.
â¢âevelop and use tools to better predict the risks of new and existing chemicals in the environment, including toxicity,
D
fate, and transport.
â¢âuantify and document the life-cycle consequences associated with producing commonly used resources and products
Q
and the broad costs and benefits of alternative approaches designed to reduce pollution and waste. Work with social
and behavioral scientists to communicate this information to inform the decisions of consumers, manufacturers, and
governments that could incentivize these efforts.
â¢â anage or remediate existing legacy hazardous waste and contaminated sites to eliminate harmful exposures and return
M
sites to productive use.
Capturing the Value of Waste:
â¢âuantify waste-stream characteristics and identify opportunities to reuse or recover materials traditionally considered as
Q
waste
Identify products that could be manufactured with recycled and reused materials that would have lower cost, lower
â¢â
greenhouse gas emissions, and require less energy to produce.
â¢âevelop new resource-recovery technologies and processes for cost-effective recovery of materials and energy from the
D
waste stream.
â¢â ork with other sectors including public health, architecture, and urban planning to integrate engineering designs,
W
processes, and technologies to develop effective approaches to resource recovery with broad societal benefits.
Design a Future Without Pollution or Wasteâ |â 53

Environmental engineers support the well-being of people and the planet in areas where the two intersect. Over the decades the field has improved countless lives through innovative systems for delivering water, treating waste, and preventing and remediating pollution in air, water, and soil. These achievements are a testament to the multidisciplinary, pragmatic, systems-oriented approach that characterizes environmental engineering.

Environmental Engineering for the 21st Century: Addressing Grand Challenges outlines the crucial role for environmental engineers in this period of dramatic growth and change. The report identifies five pressing challenges of the 21st century that environmental engineers are uniquely poised to help advance: sustainably supply food, water, and energy; curb climate change and adapt to its impacts; design a future without pollution and waste; create efficient, healthy, resilient cities; and foster informed decisions and actions.

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